We studied the formation of a composite from an aqueous dispersed medium with albumin and carbon nanotubes under the action of laser radiation in continuous wave (CW) mode and pulsed mode with a repetition rate of 10 Hz and pulse duration of 16 ns. During the experiments, the temperature was monitored at the site of exposure, as well as its distribution in the liquid. Pulsed solid-state Nd:YAG laser and CW diode laser with an irradiation power of ∼500  mW were used as radiation sources. However, a three-dimensional composite was formed only with constant exposure. The effect of pulsed laser radiation with an intensity corresponding to nonlinear interaction with water dispersion led only to its enlightenment. Thus, it is important not only the energy parameters of radiation but also the frequency of energy portions exposure for the fabrication of tissue-engineered structures (composites). As a result, it was found that the curing of the dispersion and the composite formation occurs under the action of continuous or pulsed (with a high pulse repetition rate) laser radiation at a temperature in the range from 45°C to 50°C; in case the pulse repetition rate is insufficient, composite formation is not observed even under the action of high intensity radiation and heating occurs only to a temperature of ∼40  °  C. This formation process can be generated both in the visible 532 nm and in the infrared 810-nm wavelength ranges. In this case, one of the main conditions is the absence of albumin or cells absorption at these wavelengths so that absorption occurs mainly with single-walled carbon nanotubes. Studies of the surface and internal structure of the composite made it possible to demonstrate the binding of nanotubes to each other. This happened under the influence of laser radiation. This led to high hardness values of the composites. The average value of hardness was 0.26  ±  0.02  GPa.

An experimental setup with a laser fiber optic probe has been developed, and the vibration dynamics of the vocal folds (VFs) in the larynx of rabbits have been studied. VF vibrations were excited by a variable pressure air stream. We found that, at an air flow pressure of 50 to 60 mm Hg, VFs generate a white vibration noise in the frequency range of 100 Hz to 10 kHz. The spectrum of excited vibration frequencies becomes narrower when the air flow pressure decreases from 10 to 20 mm Hg, and three discrete lower fundamental frequencies of intrinsic mechanical vibrations of individual VFs are excited at about 360, 750, and 1100 Hz, simultaneously with narrow peaks in the high-frequency region at about 3, 6, and 8 kHz, respectively. The characteristic discrete vibration frequencies of VFs are most efficiently excited near the air flow exhaustion at a pressure of 1 to 5 mm Hg. We detected a difference in the fundamental frequencies of the excited vibrations between intact VF and those treated for a scar defect in one of the VFs. The frequencies of the lowest intrinsic excited modes of the treated VF are slightly higher compared with untreated (intact) VF. The increase in the vibration frequencies may be explained by the growth of VF’s stiffness related to the formation of scar tissue. The mentioned frequency difference was registered with confidence and may serve as a basis for a mildly invasive instrumental diagnostics in the therapy of VF disorders as an aid to a traditional examination and subjective assessment of VF states.

Mesenchymal stem cells (MSCs) represent a significant interest for cell therapy applications and, being primary cells, undergo gradual aging in culture. We studied the effects of low-intensity infrared laser irradiation during aging of MSCs in culture. Both young and aged MSCs respond to low irradiation doses (0.17  J  /  cm²) by growth activation and to middle doses (2.1  J  /  cm²) by growth retardation. Aged cells demonstrate a relatively higher growth response to low doses, but they are significantly more susceptible to deleterious effects of middle doses compared to young cells. Studies of MSC aging during long-term culture under hypoxia conditions demonstrate that low-dose irradiation of MSCs every 2 days in culture substantially increases the number of population doublings, compared to the control group. In addition, irradiated cells persisted in culture for two passages (4 days) longer than their control counterparts. However, irradiated cells did not proliferate more rapidly if irradiation was omitted. We conclude that growth responses of young and aged murine MSCs to infrared laser irradiation differ significantly and that regular irradiation affects MSC aging in culture but does not result in a bonafide retardation of aging process.